Twin T circuit wanted
in [Design]
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From: John Fields on 11 Jun 2010 09:03 On Thu, 10 Jun 2010 19:59:50 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On 10 Jun 2010 17:55:23 -0700, Winfield Hill ><Winfield_member(a)newsguy.com> wrote: > >>John Larkin wrote... >>> >>> I have never called myself a "judge", and Win has never called >>> himself a "master." You and JT call us that, so you can then >>> abuse us for saying things we never said. How lame. >> >> That's correct. I work hard at what I do, but I'm always >> on the lookout for mistakes I may make, or more often, >> things I don't yet understand. Hopefully I'll not pipe >> up about something I don't yet understand, but oops, oops, >> sometimes one doesn't yet know that they don't understand >> something, or they may just make a silly thoughtless mistake. > >A lot depends on how fragile your ego is. If you are determined to >always be "right" in public, or you are determined that someone else >is always wrong, you'll be a fathead and not learn anything. > >Of course, there are some people who are AlwaysWrong. --- Unbelievable!!! You hoist yourself on your own petard and you don't even know it.
From: John Larkin on 11 Jun 2010 10:49 On Fri, 11 Jun 2010 18:23:38 +1000, Grant <omg(a)grrr.id.au> wrote: >On Thu, 10 Jun 2010 18:11:44 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 10 Jun 2010 17:21:02 -0700 (PDT), MooseFET >><kensmith(a)rahul.net> wrote: >> >>>On Jun 11, 12:01 am, John Larkin >>>[....] >>>> I don't think so. People designed radar, magnetrons and klystrons and >>>> waveguides and servos and all that, without computers. They did the >>>> math. Early computers were obviously designed without help from >>>> computers. >>> >>><PITA> >>>Make that "electronic computers". At one time, a computer was >>>a person who computed. Companies had rooms full of people >>>grinding through the numbers to make sure that the sums were >>>right. >>></PITA> >> >> >><OLDFARTSTORY> >> >>My first real job was a research assistant in microwave spectroscopy, >>a summer tech job. Two grad students on the same project spent the >>entire summer hunched over a Friden calculator in a small room, >>calculating rotational resonances for some organic thing. My PC could >>do all that now in, probably, a millisecond. >> >></OLDFARTSTORY> >> >> >> >>> >>>There were also some analog computers and mechanical >>>computers. Each generation has used the tools made by >>>the previous. Just try to imagine designing with Roman >>>numerals and not even a slide rule. >>> >>> >>>> I don't use Spice a lot, and could certainly get along without it. It >>>> is helpful when evaluating nonlinear systems, where math solutions >get messy. >>> >>>I use spice as a sanity check. Sometimes it even finds some. >>> >>>LTSpice is also nice for making a schematic to email to someone. >> >>It is just about the only portable schematic format the industry has >>ever seen. Not a bad editor, but the circuits seem to wander all over >>the screen as you zoom. I have to keep selecting my whole circuit and >>dragging it back into sight. > >Minor problem, return for full refund? :) > Somebody should create a component "pushpin" so I can nail the sucker down. John
From: John Larkin on 11 Jun 2010 10:58 On Fri, 11 Jun 2010 07:45:40 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On 10 Jun 2010 17:55:23 -0700, Winfield Hill ><Winfield_member(a)newsguy.com> wrote: > >>John Larkin wrote... >>> >>> I have never called myself a "judge", and Win has never called >>> himself a "master." You and JT call us that, so you can then >>> abuse us for saying things we never said. How lame. >> >> That's correct. I work hard at what I do, but I'm always >> on the lookout for mistakes I may make, or more often, >> things I don't yet understand. Hopefully I'll not pipe >> up about something I don't yet understand, but oops, oops, >> sometimes one doesn't yet know that they don't understand >> something, or they may just make a silly thoughtless mistake. > >--- >Typical Larkinese tactic; poisoning the well. > >Better watch out, Win, if you disagree with him he'll more than likely >have something nasty and untrue to say about you, too. I have two copies of his book, one at work and one at home, and I give one to every intern who doesn't already have one. I've learned a lot from his book and his occasional postings (is 3e done yet?) and I'm happy to discuss circuits with him. "Discuss" means just that, play with ideas, diverge and converge, brainstorm, tell stories, get stupid, evolve things. Try it some time: it's fun. Some people can play this game, some can't. John
From: John Larkin on 11 Jun 2010 11:00 On Fri, 11 Jun 2010 07:41:33 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Thu, 10 Jun 2010 17:44:54 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 10 Jun 2010 19:03:28 -0500, John Fields >><jfields(a)austininstruments.com> wrote: >> >>>On Thu, 10 Jun 2010 15:53:53 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Thu, 10 Jun 2010 12:50:00 -0700 (PDT), dagmargoodboat(a)yahoo.com >>>>wrote: >>>> >>>>>John Larkin wrote: >>>>>> dagmargoodb...(a)yahoo.com wrote: >>>>>> >>>>>> >On Jun 9, 9:18 pm, Winfield Hill wrote: >>>>> >>>>>> >> Picky, picky. To my mind, the base current robbed by the >>>>>> >> collector starves the base, lowering the CE stage's gain, >>>>>> >> until the exact equilibrium is achieved. ALC, AGC, pick >>>>>> >> your name as you like. Either way it gets the job done >>>>>> >> rather nicely, and is a bit different from what we've seen >>>>>> >> elsewhere, such as in old radio circuits. I see that it >>>>>> >> has been analyzed as a possible RF oscillator technique. >>>>>> >> But it seems to me that, working as we imagine, Vce(sat) >>>>>> >> and all, this trick would be limited to far far below fT. >>>>>> >>>>>> >Just to clarify, the RF versions I posted are similar to, but not the >>>>>> >same as John's. �They're standard UHF designs, Class A, without John's >>>>>> >precision AGC. �I don't think they can use John's AGC method directly-- >>>>>> >if saturated, the transistors would be too slow--but maybe a Baker-ish >>>>>> >clamp thing would do the job. >>>>>> >>>>>> In my oscillator, a c-b schottky diode would keep the transistor c-b >>>>>> junction from conducting, and keep the transistor out of saturation. >>>>>> Tempco would still be low. That simplifies things considerably. Not >>>>>> bad. >>>>> >>>>>Good idea. >>>>> >>>>>> >Oh, and John's oscillator really swings ~ 2* (Vcc + Vbe), not 2* (Vcc >>>>>> >- Vbe). �Reason being, the AGC operates as the average base voltage >>>>>> >gets sucked down to near 0v, killing the gain. >>>>>> >>>>>> I seem to recall the DC base voltage being about +.6. So the collector >>>>>> swings to just about zero, and the AC output is 2*Vcc p-p. Somebody >>>>>> could Spice this, if they were interested, and see exactly what >>>>>> happens. >>>>> >>>>>I Spice'd all the circuits I posted. >>>>> >>>>>> The transformer ratio gets involved some, too. >>>>> >>>>>Yep, but to a 1rst order: average emitter voltage = 0, ignore the >>>>>swing 'cause it's small, and that gets you pretty close. V(b) = 120mV >>>>>in my 5KHz example. >>>>> >>>>>James >>>> >>>>How much p-p voltage on the emitter? >>>> >>>>That low a DC base voltage suggests more like class-C action. With >>>>less turns on the emitter winding, the thing gets more class A-ish, >>>>and I'd expect the DC base voltage to go up some. I think. >>>> >>>>I wonder what happens to the DC base voltage as the base bias resistor >>>>changes. I'm not even sure which direction things will go. >>>> >>>>Complicated, for 5 parts. >>> >>>--- >>>So, _there's_ a "circuit designer" who can't even figure out how a >>>circuit which he's put into the world works, >> >>It works fine the way I designed it to work. I admit I don't >>understand all the possible variations, and the entire possible >>operating envelope, because it didn't matter 35 years ago, and it >>doesn't matter now. It's just sort of interesting to discuss. >> >>Discussion sort of requires that you don't assume you know everything. >> >> >> and yet wants to elevate >>>himself into the position of a judge of circuit designs? >> >>I have never called myself a "judge" > >--- >Perhaps not in so many words, but your neverending patting yourself on >the back while demeaning the work of others speaks volumes about what >you perceive yourself to be. >--- > >>, and Win has never called himself >>a "master." You and JT call us that, so you can then abuse us for >>saying things we never said. > >--- >I've never called you a judge and I've never called Win a master, so >it seems _you're_ the one putting words in my mouth so you can create >a straw man, you insidious trash. >--- > >>How lame. > >--- >PKB, cheater. >--- > >>Tell us more about tuning fork oscillators. > >--- >Why, when all you're interested in is generating another row? > >Forget it; I'm done with you for the time being. Can you quantify that? Round off the the nearest millisecond. John
From: John Larkin on 11 Jun 2010 11:02
On Thu, 10 Jun 2010 22:34:33 -0700 (PDT), dagmargoodboat(a)yahoo.com wrote: >On Jun 10, 11:45�pm, dagmargoodb...(a)yahoo.com wrote: >> John Larkin wrote: >> > dagmargoodb...(a)yahoo.com wrote: >> > >John Larkin �wrote: > >> > >> The transformer ratio gets involved some, too. >> >> > >Yep, but to a 1rst order: average emitter voltage = 0, ignore the >> > >swing 'cause it's small, and that gets you pretty close. �V(b) = 120mV >> > >in my 5KHz example. >> >> > How much p-p voltage on the emitter? >> >> 1 volt. �That might be a bit hot, as I noted in the post. �I did that >--^^^^^^ > >Ooops. That was for another sim, which uses 1mH and 10uH. The posted >5 KHz ckt used 1mH / 25uH, so the emitter swing was about 1.8v p-p. > >James Arthur That's savage. John |